My rectitude (8)
I believe the answer is:
goodness
This clue is a double definition.
'my' is the first definition.
(I've seen this before)
'rectitude' is the second definition.
(thesaurus)
(Other definitions for goodness that I've seen before include "Exclamation of surprise" , "Morality, generosity, kindness" , "Boy" , "Virtue, rightness" , "Moral excellence" .)